Learning Forum

[mehran]

1 - Can someone please tell me what's the recommended FDTD simulation length for a given pulse length?

2 - Do we need to "add mesh" or the default mesh structure should work? (I know it depends on the structure, but in general for simple tasks. For example for a layered (nonlinear/linear) dielectric structure, Yu-Mittra method 2 should be fine? )

 

[Guilin Sun]

A1: if you do not know the pulse length or no specific requirement, or not having issues, please use the default settings.

A2: you may not need to use the override mesh. Please refer this post https://forum.ansys.com/forums/topic/ansys-insight-about-override-mesh-in-fdtd-solutions-its-use-and-settings/

for general interface, no need to use override, in most cases. When you have 2D thin sheet, you may need, but it is also not mandatory, and this is for resolution, not specifically for interface.

[mehran]

Thank you for getting back to me on this. I do know the input pulse length. I am using various pulse lengths (100, 200, 500) fs. Can you please tell me what's the desired length for these, for example maybe 10 times the pulse-legnth? 

[Guilin Sun]

Do you have specific requirement for the pulse length? if not, please use the default signal, which is optimized. In particular, for linear simulation, no need to change the pulse length, except you want to have narrow bandwidth or there is resonance outside the desired bandwidth that prevents fast convergence.

 

Only when you want time-domain, accumulate effect then you need to set the pulse length to be practical, which is rare.

For nonlinear simulation, it might be different, depending on what the  nonlinear effect you simulate. In some case you have to use almost sine excitation: https://optics.ansys.com/hc/en-us/articles/360042192813

other articles might be useful :

https://optics.ansys.com/hc/en-us/articles/360043165194-Nonlinear-optics-list-of-examples

https://optics.ansys.com/hc/en-us/articles/360034394234-Understanding-frequency-domain-CW-normalization

https://optics.ansys.com/hc/en-us/articles/360034383094-Changing-the-source-bandwidth-in-FDTD-and-MODE